Re: Compatibility aliases, defsubsts, and macros...

[Miles Bader]

2006/1/31, Bill Wohler <address@hidden>:
> > #2 is very important; the bad old practice of just defining the
> > standard functions on systems which didn't have it built in (as you
> > demonstrate) caused many problems.
>
> Just out of curiosity, do you remember the problems?

It intereferes with other packages that are trying to test the
environment by probing the existance or non-existance of certain
functions.  So while it may work fine with just _one_ such package
installed, as soon as you try to load the next one, things blow up. 
Well, usually not "blow up", but instead subtle and hard-to-diagnose
misbehavior.

[If all packages (1) _only_ used function testing on a
function-by-function basis, and (2) defined subsitute definitions
which were perfectly functional, and (3) did not use function testing
for any purpose other than defining a single replacement function,
_then_ it might all work -- but these conditions are most definitely
not satisfied by many packages out there, and even a single package
can cause grief for all the others loaded with it.]

w3 is probably the most famous case of code that used this practice
and caused problems as a result.

-miles
--
Do not taunt Happy Fun Ball.